Explosive composition containing a glycol and a hydroxy alkyl ether of a polysaccharide

ABSTRACT

A SUBSTANTIALLY NON-AQUEOUS EXPLOSIVE SLURRY COMPOSITION COMPRISING ESSENTIALLY A SUSPENSION OF INORGANIC OXYGEN-SUPPLYING SALT IN A FLUID MATRIX, SAID FLUID MATRIX COMPRISING AT LEAST ONE LOWER ALIPHATIC GLYCOL SELECTED FROM THE GROUP CONSISTING OF ETHYLENE GLYCOL, DIETHYLENE GLYCOL, PROPYLENE GLYCOL AND DIPROPYLENE GLYCOL THICKENED WITH A MATERIAL AND HYDROXYPROPYL ETHERS OF POLYSACCHARIDES AND MIXTURES THEREOF.

United States Patent 3,741,833 EXPLOSIVE COMPOSITION CONTAINING A GLYCOL AND A HYDROXY ALKYL ETHER OF A POLYSACCHARIDE Errol Linton Falconer, Mont Saint-Hilaire, Quebec, Canada, assignor to Canadian Industries Limited, Montreal, Quebec, Canada No Drawing. Filed Feb. 29, 1972, Ser. No. 230,521 Int. Cl. C06b N04 US. Cl. 149-109 5 Claims ABSTRACT OF THE DISCLOSURE A substantially non-aqueous explosive slurry composition comprising essentially a suspension of inorganic oxygen-supplying salt in a fluid matrix, said fluid matrix comprising at least one lower aliphatic glycol selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol thickened with a material selected from the group consisting of hydroxyethyl and hydroxypropyl ethers of polysaccharides and mixtures thereof.

This invention relates to thickened explosive slurries. In particular the invention relates to slurry explosives which are devoid of any Water phase.

Explosive slurries, such as those described in United States Patent No. 2,930,685 issued to M. E. Cook and E. Farnham on Mar. 29, 1960 are now widely employed in the mining and construction industries. These explosive compositions comprise ammonium nitrate and other oxygen-supplying salts dispersed in a thickened aqueous phase and may be sensitized with particulate self-explosives such as TNT or may contain added sensitizer/fuel material such as powdered light metals. The products may be prepared in a range of thickness or consistencies by the judicious use of water-gelling agents and, because of the flowable character of the slurries, they may be pumped in bulk form directly in the boreholes without previous packaging in containers. Aqueous explosive slurries are both safe and powerful and their use has had great beneficial effect on blasting technology in recent years.

The quantity of waternormally employed in the formulation of explosive slurries generally is in the range of from about 5% to about 30% by weight of the total slurries. The amount of water employed in a slurry com position will depend on the desired fiowability and on the kinds of ingredients present in the mixture. Smaller quantities of water may be used where a highly viscous product is to be used in, for example, wet boreholes while larger volumes of water are used in less thick and more easily pumpable products. The thickening of the aqueous phase of the slurry is accomplished by adding to the Water one or more of a number of water soluble or miscible inert thickeners such as a hydrophilic colloid like guar gum or starch and the like. Generally the aqueous gelphase is made sufliciently viscous so that the added solid undissolved ingredients will not settle out during periods of storage. The addition of cross-linkers can also be made to provide an aqueous gel of visco-elastic consistency.

While the aqueous slurries of both the thick viscous type and the more fluid pourable type are of great value as efficient, safe and economic blasting agents, the presence of water therein detracts considerably from their explosive power and, in the case of packaged slurries, generally requires the use of relatively expensive waterproof packaging. It may be seen therefore that the elimination of water from slurry explosives is a desirable objective.

It is the primary object of this invention to provide substantially non-aqueous explosive slurry compositions of ice improved properties. Additional objects of the invention will appear hereinafter.

By substantially non-aqueous explosive slurry compositions are meant explosive compositions containing less than about 4% water by weight as an ingredient, including the small quantities of water present as water of crystallization in the salts.

It has indeed been found that explosive slurry compositions comprising essentially one or more oxygen-supplying salts dispersed in a thickened fluid matrix or phase may be provided in non-aqueous form if the thickened fluid phase consists essentially of at least one lower aliphatic glycol thickened with an additive selected from the group consisting of hydroxyethyl and hydroxypropyl ethers of polysaccharides and mixtures thereof. It is thus possible to convert the inexpensive lower aliphatic glycols into useful non-aqueous gels capable of being used as a fluid matrix in explosive slurries.

The lower aliphatic glycols employed as the gel-phase fluid matrix of the slurries of the present invention possess solubility properties towards the oxygen-supplying salts such as calcium, ammonium and sodium nitrates and sodium, calcium and ammonium perchlorates as well as towards soluble fuels such as urea and formamide and mixtures thereof. The substantially non-aqueous explosive slurry compositions of the invention thus comprise essentially a suspension of inorganic oxygen-supplying salt in a fluid matrix, said matrix comprising at least one lower aliphatic glycol selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol thickened with a material selected from the group consisting of hydroxyethyl and hydroxypropyl ethers of polysaccharides and mixtures thereof.

While a number of polymeric and other colloidal thickeners for fluids are known and may be partly effective in thickening or gelling lower aliphatic glycols, these are generally unsuitable for use in conjunction with the oxygeu supplying salts found in explosive slurries. For example, the inorganic colloidal thickeners such as pyrogenic silica results in unsatisfactory explosive products in terms of stability. Soluble polymers such as polyoxyethylene resins are salt sensitive and are precipitated in the presence of dissolved oxygen salts. Only the series of the hydroxyethyl and hydroxypropyl ethers of polysaccharides have been found capable of providing non-exuding stable glycol gels in the presence of oxygen-supplying salts such as ammonium, sodium and calcium nitrates and perchlorates. The quantity of thickener employed with a given quantity of lower glycol is arbitrary and depends on the degree of thickness or plasticity desired. Generally from 0.2% to 10.0% by weight of thickener in the glycol can be used although the higher level will most often be beyond the degree of gelation normally useful in commercial slurry explosives.

Examples of polysaccharides the hydroxyethyl and hydroxypropyl ethers of which are suitable for use as thickener are glucose polysaccharides, mannose polysaccharides and galactose polysaccharides.

The following examples and table illustrate the thickened glycol gel-phase of the invention and will show the desirable properties of slurry explosive compositions containing the same.

EXAMPLE 1 Two gelling tests A and B were undertaken to evaluate the ability of several hydroxyalkyl ethers of polysaccharides to thicken ethylene glycol.

In test A, 10 grams of ethylene glycol and 1 gram of a polysaccharide derivative were mixed with stirring at room temperature in the presence of 5 grams each of sodium nitrate and ammonium nitrate which nitrates are typical of those found in commercial slurry explosive compositions.

A plastic-like self-supporting gel was formed as follows:

with hydroxyethyl guar, after 5 minutes; with hydroxypropyl guar, after minutes; with hydroxyethyl cellulose, after 30 minutes.

In test B, a salt-containing glycol-based liquor was prepared by dissolving 60 parts of technical grade calcium nitrate and 30 parts of ammonium nitrate in 55 parts of ethylene glycol, 23 parts of diethylene glycol and 25 parts of formamide. All salts were fully dissolved at room temperature. About one gram of a polysaccharide derivative was added to about 10 grams of the glycol-based liquor. Plastic-like self-supporting gels were formed as follows:

with hydroxyethyl cellulose, after 3 minutes; with hydroxyethyl guar, after 6 minutes; with hydroxypropyl guar, after minutes.

Observation of the results of tests A and B emphasizes the unpredictability of the influence of soluble salts on the rates at which the gelling of the ethylene glycol liquor phase takes place. It can be observed, that hydroxyethyl cellulose in test A produced a gelled glycol in 30 minutes in the presence of ammonium and sodium nitrate, while in test B the same derivative produced a gel in about 3 minutes in the presence of calcium and ammonium nitrate and formamide. It was generally observed that the guar derivatives produced a clearer gel than did the cellulose derivatives. The degree of gelation and the time in which it occurs is also effected by the degree of substitution (D.S.) as outlined by W. A. Jordan in US. Pat. No. 3,483,121 issued on Dec. 9, 1969.

In similar tests, propylene glycol and diethylene glycol were gelled by the addition of hydroxyethyl guar and hydroxypropyl guar. Hydroxypropyl cellulose and hydroxyethyl starch were found capable of gelling glycol solutions of oxidizer nitrate salts. Suprisingly it was noted that hydroxypropyl guar did not gel pure glycol. Only when an ammonium salt was dissolved in the glycol did the hydroxypropyl guar produce effective thickening. Most of these thickening agents are generally available from commercial suppliers, but, if desired, may be prepared in the laboratory or factory. Hydroxyethyl starch, for example, may be made by reacting equimolar portions of corn starch, 2-chloroethanol and sodium hydroxide in the presence of isopropanol. This preparation is typical of the preparation of hydroxyethyl derivatives of polysaccharide compounds described in the chemical literature.

The following example and tables demonstrate the utility of the glycol fluid matrix of the invention in the preparation of pourable or pumpable slurry explosive composition. As noted heretofore, most slurry explosive compositions comprise a mixture of oxygen-supplying salt, sensitizer and fuel ingredients dispersed in a thickened water matrix or carrier. Since it is known that the presence of water decreases the strength of explosive formulations, it is desirable to replace the water in slurry explosives. Heretofore, however, it has not been possible to find a suitable fluid carrier which could be modified or thickened adequately in the presence of oxidizer salts without either undesirable side effects which were disadvantageous or without excessively high cost.

EXAMPLE 2 An ethylene glycol-based liquor containing dissolved oxygen-supplying salts, a small quantity of hydroxyethyl guar or hydroxypropyl guar and other minor glycol-soluble ingredients useful in slurry formulations, was prepared. To this glycol-base liquor was added a substantial quantity of prilled ammonium nitrate and a further quantity of hydroxyethylor hydroxypropyl guar. After mixing in a mechanical mixer and just before pouring into pickages, a small quantity of a liquid cross-linker was added. The composition of two typical slurry formula tions are shown in Table I where the proportions given are in percent by weight.

TABLE I Formulations A. Liquor ingredients (partly thickened) 1 Ethylene glycol 17.0 Formamide Water Urea Calcium nitrate (technical). Ammonium nitrate Sodium nitrate Ammonium lignosulphonate Dodecylamine acetate Hydroxyethyl guar or hydroxypropyl guar. 0. 15 0. 1

B. Dry ingredients:

Prilled ammonium nitrate 41. 1-. 9 Hydroxyethyl or hydroxypropyl guar- 0.2 0.

0. Liquid cross-linker:

Sodium dichromate/Ierric nitrate 0. Density at 70 F Consistency Unccnfincd critical diametern at 40 F 1 3 detonated at a low order and was considered defiagration.

An examination of the compositions and results shown in Table I will demonstrate the ability to prepare powerful, non-aqueous glycol-base fluid matrix slurries of excellent sensitivity. Expensive sensitizing ingredients such as TNT, smokeless powder, aluminum, amine nitrates and alkanolamine nitrates and the like are not required for the attainment of useful sensitivities for the use of the slurry in large diameter charges or bulk operations. However. if a further enhancement of sensitivity is required, the addition of sensitizing ingredients may be made.

A glycol-based gel-phase slurry of enhanced sensitivity is shown in Table II below, where the proportions given are in percent by weight.

TABLE II (A) Liquor ingredients (partly thickened):

0. 4 1. l8 Cross-linked 1. gel

Ethylene glycol Formamide 3.0 Calcium nitrate (technical) 8.0 Ammonium nitrate 6.0 Methylamine nitrate 18.0 Surfactant 0.2 Hydroxypropyl guar 0.3 (B) Dry ingredients:

Ammonium nitrate 41.0 Sodium nitrate 17.1 Hydroxypropyl guar 0.6 Consistency Thick slurry Density at 70 F. (g./cc.) 1.12 Cartridge diameter inch 1 Velocity of detonation with 10 gram pentolite initiation meter/sec. 233

As demonstrated herein, the non-aqueous slurry of the invention comprises an oxygen-supplying salt or mixture of oxygen-supplying salts dispersed in a fluid matrix of a solution of the salts in a thickened lower glycol. Added fuel and or sensitizing materials may also be dispersed in the fluid matrix. The particular advantage of the slurry explosive of the invention is that the use of water as a component in the system is avoided and is replaced by a lower glycol which functions both as a fluid matrix and a fuel and hence provides added energy during detonation. While the use of glycol as a fuel component in aqueous slurry explosives is known and has been disclosed elsewhere, the complete elimination of water and its replacement by a thickened lower glycol in explosives slurries of a pumpable or pourable consistency has not heretofore been proposed. The density of the slurry described herein will be less than 1.8 grams per cm.

What I claim is:

1. A substantially non-aqueous explosive slurry composition comprising essentially a suspension of inorganic oxygen-supplying salt in a fluid matrix, said fluid matrix comprising at least one lower aliphatic glycol selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol thickened with a material selected from the group consisting of hydroxyethyl and hydroxypropyl ethers of polysaccharides and mixtures thereof.

2. An explosive composition as claimed in claim 1 wherein the polysaccharide is selected from the group consisting of glucose polysaccharides, mannose polysaccharides, galactose polysaccharides and mixtures thereof.

3. An explosive composition as claimed in claim 1 also containing a fuel ingredient.

4!. An explosive composition as claimed in claim 1 also containing a sensitizer.

5. An explosive composition as claimed in claim I having a density of less than 1.8 grams/cc.

References Cited UNITED STATES PATENTS STEPHEN I. LECHERT, IR., Primary Examiner US. Cl. X.R. 

